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Communication | Regular issue | Vol 4, No. 8, 1976, pp.1361-1366
Published online, 1st January, 1970
DOI: 10.3987/R-1976-08-1361
■ Cycloaddition of 2-Phenyl-3-ethoxycarbonyl-Δ2-pyrroline-4,5-dione with Butadiene. Evidence of [1,3]Sigmatropy for Formation of the Diels-Alder Product

Takehiro Sano and Yoshisuke Tsuda*

*Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

Thermal and photochemical cycloaddition of 2-phenyl-3-ethoxycarbonyl-Δ2-pyrroline-4,5-dione (1) with butadiene afforded the same 1,2-adduct (2) in reglo- and stereoselective manner. At elevated temperature the 1,2-adduct (2) changed by an 1,3-sigmatropic shift into the normal Dlels-Alder adduct (3). The easiness of sigmatropy was greatly influenced by the nature of N-substituents and decreased by the following order : H > Me > Ph. In case of N-phenyl derivative, the rearrangement was not observed.